Skip to main content
Biology LibreTexts

4.0: Mutation and Polymorphism

  • Page ID
    27244
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    We have previously noted that an important property of DNA is its fidelity: most of the time it accurately passes the same information from one generation to the next. However, DNA sequences can also change. Changes in DNA sequences are called mutations. If a mutation changes the phenotype of an individual, the individual is said to be a mutant. Naturally occurring, but rare, sequence variants that are clearly different from a normal, wild-type sequence are also called mutations.On the other hand, many naturally occurring variants exist for traits for which no clearly normal type can be defined; thus, we use the term polymorphism to refer to variants of DNA sequences (and other phenotypes) that co-exist in a population at relatively high frequencies (>1%).

    Fig4.2.png
    Figure \(\PageIndex{1}\): Examples of wild-type (A) and mutant (B) mouse embryos observed while screening for genes affecting cranium development.(PLoS Biology- Zarbalis, K. et al (2004) PLoS Biology-PD)

    Polymorphisms and mutations arise through similar biochemical processes, but the use of the word “polymorphism” avoids implying that any particular allele is more normal or abnormal. For example, a change in a person’s DNA sequence that leads to a disease such as cancer is appropriately called a mutation, but a difference in DNA sequence that explains whether a person has red hair rather than brown or black hair is an example of polymorphism. Molecular markers, which we will discuss in Chapter 9, are a particularly useful type of polymorphism for some areas of genetics research.


    This page titled 4.0: Mutation and Polymorphism is shared under a CC BY-SA 3.0 license and was authored, remixed, and/or curated by Todd Nickle and Isabelle Barrette-Ng via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.